The disclosure of the present application relates to a battery pack for connecting a plurality of batteries.
Recently, portable electronic devices such as a notebook personal computer, a mobile phone and a PDA (Personal Digital Assistants) have been spread and a lithium ion secondary battery having advantages such as high voltage, high energy density and light weight structure has been widely utilized as a power supply of such electronic devices.
In a notebook computer, for example, a cylindrical type lithium ion secondary battery using a electrolytic solution as an electrolyte is typically used, and these days the usage opportunity of a gel polymer electrolyte obtained on impregnating a polymeric material with a non aqueous electrolytic solution a flattened type lithium-ion polymer secondary battery using an all-solid polymer electrolyte, etc. is increasing.
A lithium ion polymer secondary battery has a cathode, an anode, and a polymer electrolyte, and includes a battery cell of which battery elements being lead out respective terminal of cathode and anode are coated with such as external film. In addition, the battery pack is configured to he accommodated in a box type plastic mold case including, for example, an upper case and a lower case, together with a circuit substrate on which a battery cell and a circuit are mounted.
It is desired to make a large capacity battery pack in an electronic device such as a notebook computer, so that the electronic device can be used for a long time. Accordingly, a battery pack which is connected a plurality of same type battery cells in parallel in order to increase the capacity of the battery pack.
Now, a conventional battery pack 100 is briefly explained with reference to figures. Referring to FIG. 1 and FIG. 2, a plurality of flattened type battery cells 102 are arranged in the conventional battery pack 100, which is constructed that a cathode terminal 111a and an anode terminal 111b (hereinafter electrode terminal 111 otherwise showing a specified electrode terminal) of each battery cell 102 are connected to a circuit substrate 103 to be accommodated in an enclosure such as a housing including an upper case and a lower case.
The battery cell 102 is constructed to be accommodated in a soft laminated film where for example battery elements are formed in rectangular, and wall portions 105 are formed by bending the laminated film. And on a surface surrounded by the wall portions 105, a drawer portion 104 which leads out electrode terminals is formed.
As described above, a battery cell for accommodating battery elements in a laminated film having wall portions at its sides by bending the laminated film is described in Japanese Unexamined Patent Application Publication No. 2000-156208.
A charge and discharge control FET (Field Effect Transistor), a protective circuit including IC (Integrated Circuit) for monitoring a secondary battery and controlling the charge and discharge control FET, a connector for connecting to an external element, and so on are mounted on the circuit substrate 103. Furthermore, a contact member 112 for connecting to the electrode terminal 111 is provided at the circuit substrate 103.
There are various shapes and sizes of the battery pack 100 depending on an electronic device which uses the battery pack 100. In other words, the shape and the size of the battery pack 100 is determined in accordance with the shape and the size of the space in the electronic device where the battery pack 100 is accommodated. Moreover, since the shape and the size of the battery cell 102 is defined according to its charge and discharge capacity and its charge and discharge current volume, the shape and the size of the circuit substrate 103 is determined based on the shape and the size of the battery pack 100 and the battery cell 102.
Therefore, when the battery cell 102 is connected to the circuit substrate 103, there may be a case where the electrode terminal 111 cannot be directly connected to a contact member provided on the circuit substrate 103. In this case, the battery cell 102 and the circuit substrate 103 are electrically connected via relay tab 101 in the manner that the electrode terminal 111 and a relay tab 101 are connected, and then the relay tab and the circuit substrate 103 are connected. For such relay tab 101, a conductive steel plate such as aluminum Al or nickel Ni is used.
It is desirable to reduce unnecessary space in the battery pack as much as possible and improve the volumetric efficiency since a battery pack used for a portable electronic device, etc. is desired to be compact as well as large capacity and high power output.
However, there was a problem that when a battery pack was constructed by arranging such plurality of battery cells, wall portions provided in the battery cell prevent the arrangement of substrate in a drawer portion, which resulted in decrease of volumetric efficiency due to unnecessary space caused by the drawer portion.
Furthermore, there was another problem that since the wiring pattern for connecting electrode terminal cannot be linearly wired over the circuit substrate 103 as shown in FIG. 2, the dimension over the circuit substrate was more than is actually required.
Moreover, the shape and the size of the circuit substrate vary depending on the shape and the size of the battery pack. In addition, the protective circuit mounted on the circuit substrate varies depending on the property of the battery cell used in the battery pack such as charge and discharge voltage, and charge and discharge current. Thus, it is difficult to divert an existing circuit substrate. That is, when a battery pack is newly designed, there was a problem that a circuit substrate has to be newly designed correspondingly, which resulted in the increase of design cost.
Additionally, when the battery cell and the circuit substrate were connected through the relay tab, there was a problem that the addition of the relay tab itself and the process for connecting the relay tab resulted in the increase of production cost.
Therefore, it is desirable to provide a battery pack which utilizes the space to improve volumetric efficiency.
Additionally, it is desirable to provide a battery pack which downsizes a circuit substrate to make the whole size compact.
Furthermore, it is desirable to provide a battery pack which can divert a circuit substrate to reduce production cost.